Laura Smith Callahan - Academia.edu (original) (raw)
Papers by Laura Smith Callahan
Although a number of combinatorial/high-throughput approaches have been developed for biomaterial... more Although a number of combinatorial/high-throughput approaches have been developed for biomaterial hydrogel optimization, a gradient sample approach is particularly well suited to identify hydrogel property thresholds that alter cellular behavior in response to interacting with the hydrogel due to reduced variation in material preparation and the ability to screen biological response over a range instead of discrete samples each containing only one condition. This review highlights recent work on cell–hydrogel interactions using a gradient material sample approach. Fabrication strategies for composition, material and mechanical property, and bioactive signaling gradient hydrogels that can be used to examine cell–hydrogel interactions will be discussed. The effects of gradients in hydrogel samples on cellular adhesion, migration, proliferation, and differentiation will then be examined, providing an assessment of the current state of the field and the potential of wider use of the gradient sample approach to accelerate our understanding of matrices on cellular behavior.
Volumetric muscle defect, caused by trauma or combat injuries, is a major health concern leading ... more Volumetric muscle defect, caused by trauma or combat injuries, is a major health concern leading to severe morbidity. It is characterized by partial or full thickness loss of muscle and its bio-scaffold, resulting in extensive fibrosis and scar formation. Therefore, the ideal therapeutic option is to use stem cells combined with bioscaffolds to restore muscle. For this purpose, muscle-derived stem cells (MDSCs) are a great candidate due to their unique multi-lineage differentiation potential. In this study, we evaluated the regeneration potential of MDSCs for muscle loss repair using a novel in situ fibrin gel casting. Muscle defect was created by a partial thickness wedge resection in the tibialis anterior (TA) muscles of NSG mice which created an average of 25% mass loss. If untreated, this defect leads to severe muscle fibrosis. Next, MDSCs were delivered using a novel in situ fibrin gel casting method. Our results demonstrated MDSCs are able to engraft and form new myofibers in the defect when casted along with fibrin gel. LacZ labeled MDSCs were able to differentiate efficiently into new myofibers and significantly increase muscle mass. This was also accompanied by significant reduction of fibrotic tissue in the engrafted muscles. Furthermore, transplanted cells also contributed to new vessel formation and satellite cell seeding. These results confirmed the therapeutic potential of MDSCs and feasibility of direct in situ casting of fibrin/MDSC mixture to repair muscle mass defects.
Combinatorial method/high throughput strategies, which have long been used in the pharmaceutical ... more Combinatorial method/high throughput strategies, which have long been used in the pharmaceutical industry, have recently been applied to hydrogel optimization for tissue engineering applications. Although many combinatorial methods have been developed, few are suitable for use in tissue engineering hydrogel optimization. Currently, only three approaches (design of experiment, arrays and continuous gradients) have been utilized. This review highlights recent work with each approach. The benefits and disadvantages of design of experiment, array and continuous gradient approaches depending on study objectives and the general advantages of using combinatorial methods for hydrogel optimization over traditional optimization strategies will be discussed. Fabrication considerations for combinatorial method/high throughput samples will additionally be addressed to provide an assessment of the current state of the field, and potential future contributions to expedited material optimization and design.
Journal of biomedical materials research. Part A, Jan 26, 2017
Many studies have utilized Irgacure 2959 photopolymerized poly(ethylene glycol) (PEG) hydrogels f... more Many studies have utilized Irgacure 2959 photopolymerized poly(ethylene glycol) (PEG) hydrogels for tissue engineering application development. Due to the limited penetration of ultraviolet light through tissue, Irgacure 2959 polymerized hydrogels are not suitable for use in tissues where material injection is desirable, such as the spinal cord. To address this, several free radical initiators (thermal initiator VA044, ammonium persulfate (APS)/TEMED reduction-oxidation reaction, and Fenton chemistry) are evaluated for their effects on the material and mechanical properties of PEG hydrogels compared with Irgacure 2959. To emulate the effects of endogenous thiols on in vivo polymerization, the effects of chain transfer agent (CTA) dithiothreitol on gelation rates, material properties, Young's and shear modulus, are examined. Mouse embryonic stem cells and human induced pluripotent stem cell derived neural stem cells were used to investigate the cytocompatibility of each polymeriz...
Acta biomaterialia, 2016
N-cadherin cell-cell signaling plays a key role in the structure and function of the nervous syst... more N-cadherin cell-cell signaling plays a key role in the structure and function of the nervous system. However, few studies have incorporated bioactive signaling from n-cadherin into tissue engineering matrices. The present study uses a continuous gradient approach in polyethylene glycol dimethacrylate hydrogels to identify concentration dependent effects of n-cadherin peptide, His-Ala-Val-Asp-Lle (HAVDI), on murine embryonic stem cell survival and neural differentiation. The n-cadherin peptide was found to affect the expression of pluripotency marker, alkaline phosphatase, in murine embryonic stem cells cultured on n-cadherin peptide containing hydrogels in a concentration dependent manner. Increasing n-cadherin peptide concentrations in the hydrogels elicited a biphasic response in neurite extension length and mRNA expression of neural differentiation marker, neuron-specific class III β-tubulin, in murine embryonic stem cells cultured on the hydrogels. High concentrations of n-cadhe...
Journal of biomedical materials research. Part A, Jan 31, 2016
Mechanotransduction in neural cells involves multiple signaling pathways that are not fully under... more Mechanotransduction in neural cells involves multiple signaling pathways that are not fully understood. Differences in lineage and maturation state are suggested causes for conflicting reports on neural cell mechanosensitivity. In order to optimize matrices for use in stem cell therapy treatments transplanting human induced pluripotent stem cell derived neural stem cells (hNSC) into lesions after spinal cord injury, the effects of Young's Modulus changes on hNSC behavior must be understood. The present study utilizes polyethylene glycol hydrogels containing a continuous gradient in Young's modulus to examine changes in the Young's Modulus of the culture substrate on hNSC neurite extension and neural differentiation. Changes in the Young's Modulus of the polyethylene glycol hydrogels was found to affect neurite extension and cellular organization on the matrices. hNSC cultured on 907 Pa hydrogels were found to extend longer neurites than hNSC cultured on other tested ...
Acta Biomaterialia, 2015
Stem cell therapies, which aim to restore neurological function after central nervous system inju... more Stem cell therapies, which aim to restore neurological function after central nervous system injury, have shown increased efficacy when a tissue engineering matrix is implanted with cells compared to implantation of the cells alone. However, much work still needs to be done to characterize materials that can be used to facilitate and direct the differentiation of implanted cells. In the current study, polyethylene glycol hydrogels functionalized with continuous Ile-Lys-Val-Ala-Val (IKVAV) concentration gradients were fabricated and utilized to systematically study and optimize the adhesive conditions for neural differentiation of mouse embryonic stem cells in two- and three-dimensional environments. The results suggest that 570μM and 60μM are the optimal IKVAV concentrations for 2D and 3D neural differentiation, respectively, to maximize mRNA expression of neuron-specific markers and neurite extension while minimizing apoptotic activities in cultured cells compared to those exposed to higher IKVAV concentrations. The combinatorial approach presented in this work demonstrates that hydrogels functionalized with bioactive peptides provide a defined and tunable platform that can be employed to characterize and improve culture conditions for superior survival, maturation and integration of implanted cells, leading to enhanced restoration of neurological function for those receiving stem cell therapies after traumatic brain and spinal cord injuries.
Biomacromolecules, Jan 5, 2015
Amino acid-based poly(ester urea)s (PEU) are high modulus, resorbable polymers with many potentia... more Amino acid-based poly(ester urea)s (PEU) are high modulus, resorbable polymers with many potential uses, including the surgical repair of bone defects. In vitro and in vivo studies have previously shown that phenylalanine-based PEUs have non-toxic hydrolytic byproducts, and tunable degradation times. Phenylalanine PEUs (poly(1-PHE-6)) have been further modified by tethering osteogenic growth peptide (OGP) to tyrosine-based monomer subunits. These OGP-tethered PEUs have been fabricated into porous scaffolds and cultured in vitro to examine their effect on differentiation of human mesenchymal stem cells (hMSCs) toward the osteogenic lineage. The influence of tethered OGP on the hMSC proliferation and differentiation profile was measured using immunohistochemistry, biochemistry, and quantitative real time polymerase chain reaction (qRT-PCR). In vitro data shows that the OGP-tethered scaffolds show enhanced BSP expression (~130-160% increase) by 2 weeks compared to control scaffolds lac...
MRS Proceedings, 2004
... Fabrication Victor J. Chen, 1 Laura A. Smith, 1 and Peter X. Ma 1-3 1 Department of Biomedica... more ... Fabrication Victor J. Chen, 1 Laura A. Smith, 1 and Peter X. Ma 1-3 1 Department of Biomedical Engineering, 2 Biologic and Materials Sciences, and ... 2001). 7. SF Yang, KF Leong, ZH Du, and CK Chua, Tissue Engineering 7 (6), 679 (2001). ...
Online, 2007
Page 1. Nanotechnologies for the Life Sciences Vol. 9 Tissue, Cell and Organ Engineering. Edited ... more Page 1. Nanotechnologies for the Life Sciences Vol. 9 Tissue, Cell and Organ Engineering. Edited by Challa SSR Kumar Copyright 8 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN: 3-527-31389-3 4 Nanofibrous Scaffolds and their Biological Effects ...
The synthesis of a 4-dibenzocyclooctynol (DIBO) functionalized polyethylene glycol (PEG) and fabr... more The synthesis of a 4-dibenzocyclooctynol (DIBO) functionalized polyethylene glycol (PEG) and fabrication of hydrogels via strain-promoted, metal-free, azide-alkyne cycloaddition is reported. The resulting hydrogel materials provide a versatile alternative in which to encapsulate cells that are sensitive to photochemical or chemical crosslinking mechanisms.
Nano-fibrous scaffolding mimics aspects of the extracellular matrix to improve cell function and ... more Nano-fibrous scaffolding mimics aspects of the extracellular matrix to improve cell function and tissue formation. Although several methods exist to fabricate nano-fibrous scaffolds, the combination of phase separation with reverse solid freeform fabrication (SFF) allows for scaffolds with features at three different orders of magnitude to be formed, which is not easily achieved with other nano-fiber fabrication methods. This technique allows for the external shape and internal pore structure to be precisely controlled in an easily repeatable manner, while the nano-fibrous wall architecture facilitates cellular attachment, proliferation, and differentiation of the cells. In this chapter, we examine the fabrication of computer-designed nano-fibrous scaffolds utilizing thermally induced phase separation and reverse SFF, and the benefits of such scaffolds over more traditional tissue engineering scaffolds on cellular function and tissue regeneration.
Wiley Interdisciplinary Reviews-Nanomedicine and Nanobiotechnology, 2009
The structural features of tissue engineering scaffolds affect cell response and must be engineer... more The structural features of tissue engineering scaffolds affect cell response and must be engineered to support cell adhesion, proliferation and differentiation. The scaffold acts as an interim synthetic extracellular matrix (ECM) that cells interact prior to forming new tissue. In this review, bone tissue engineering is used as the primary example because of our group's focus and for the sake of brevity. We focus on nano-fibrous scaffolds and the incorporation of other components including other nanofeatures into the scaffold structure. Since the ECM is comprised in large part of collagen fibers, between 50-500 nm in diameter, well-designed nano-fibrous scaffolds mimic this structure. Our group has developed a novel thermally-induced phase separation (TIPS) process in which a solution of biodegradable polymer is cast into a porous scaffold, resulting in a nano-fibrous pore-wall structure. These nano-scale fibers have a diameter (50-500 nm) comparable to those collagen fibers found in the ECM. This process can then be combined with a porogen leaching technique, also developed by our group, to engineer an interconnected pore structure that promotes cell migration and tissue ingrowth in three dimensions. To improve upon efforts to incorporate a ceramic component into polymer scaffolds by mixing, our group has also developed a technique where apatite crystals are grown onto biodegradable polymer scaffolds by soaking them in simulated body fluid (SBF). By changing the polymer used, the concentration of ions in the SBF and by varying the treatment time, the size and distribution of these crystals is varied. Work is currently being done to improve the distribution of these crystals throughout three-dimensional scaffolds and to create nano-scale apatite deposits that better mimic those found in the ECM. In both nano-fibrous and composite scaffolds, cell adhesion, proliferation and differentiation improved when compared to control scaffolds. Additionally, composite scaffolds showed a decrease in incidence of apoptosis when compared to polymer control in bone tissue engineering. Nanoparticles have been integrated into the nanostructured scaffolds to deliver biologically active molecules such as growth and differentiation factors to regulate cell behavior for optimal tissue regeneration.
Biomaterials Science, 2013
ABSTRACT Cell sourcing continues to be a significant limitation to regenerative medicine especial... more ABSTRACT Cell sourcing continues to be a significant limitation to regenerative medicine especially in neural lineages where population heterogeneity during in vitro culture prevents definitive phenotype assessment. For nearly 40 years, the biological community has worked with amine-derivated surfaces and hydrogels, especially alginate, with little quantitative assessment of how local amine concentration influences the extent of neural differentiation and neurite extension. In this manuscript we show that the local concentration of amines distinctly influences mouse embryonic stem cell (ESC) lineage commitment and the length of neurite extensions both of which are early indicators of differentiation. The well-defined amine gradients are a highly relevant tool for identifying these critical concentrations and thresholds. We feel these results will be of critical importance to researchers developing new ex vivo culture materials for neural applications as well as the community exploring nerve regeneration in vivo.
Tissue Engineering Part A, 2010
One of the major challenges to the application of human embryonic stem cells (hESCs) to the repai... more One of the major challenges to the application of human embryonic stem cells (hESCs) to the repair of defective tissues is the directed differentiation of cells into specific lineages to avoid the formation of inferior heterogeneous tissues. To accomplish this goal, the lineage-specific stem cell population needs to be isolated and optimal differentiation conditions need to be defined. In this study, homogenous hESC-derived mesenchymal stem cells (hESC-MSCs) were generated and used to construct bone tissue. The effect of osteogenic factors, including dexamethasone (Dex) and bone morphogenetic protein-7 (BMP-7), on the osteogenesis of hESC-MSCs was investigated. It was found that BMP-7 itself had little effect on the in vitro osteogenic differentiation of hESC-MSCs; however, there was a synergic effect between BMP-7 and Dex in promoting osteogenesis. The effect of osteoconductive nanofibrous polylactic acid material on osteogenesis of hESC-MSCs was also investigated. It was found that the nanofibrous matrix architecture promoted alkaline phosphatase activity and calcium deposition of cells cultured under osteogenic conditions. Based on these findings, the hESC-MSCs were cultured on threedimensional nanofibrous scaffolds in combination with Dex and BMP-7 stimulation in vitro to generate bone-like tissues. After 6 weeks of culture, highly mineralized tissues developed with specific bone marker genes expressed. These data illustrate the promise of hESC-MSCs for bone regeneration under optimal conditions.
Tissue Engineering Part A, 2009
Controlled differentiation of embryonic stem cells (ESC) is necessary to their use as a cell sour... more Controlled differentiation of embryonic stem cells (ESC) is necessary to their use as a cell source for tissue engineering or regeneration. To date, most studies have concentrated on chemical cues to direct ESC differentiation. However, during normal embryonic development, multiple factors beyond chemical cues play a role, including the extracellular matrix (ECM) in bone development. In this study, we use nanofibrous (NF) matrices to mimic the morphology of the ECM to examine the contribution of the ECM morphology to the differentiation of mouse ESC. After 12 h of differentiation culture, mouse ESC form protrusions interacting with NF matrices, while they appear not to interact with flat films. Immunofluorescence staining after 26 days of differentiation culture indicates a greater degree of differentiation for mouse ESC on NF matrices compared to flat films. Polymerase chain reaction results, also, show greater degree of osteogenic differentiation on NF matrices compared to flat films when osteogenic supplements are added to the culture. Overall, these results demonstrate that NF morphology contributes to the controlled differentiation of mouse ESC.
Colloids and Surfaces B: Biointerfaces, 2004
Biomaterials, 2013
End-functional PLLA nanofibers were fabricated into mats of random or aligned fibers and function... more End-functional PLLA nanofibers were fabricated into mats of random or aligned fibers and functionalized post-spinning using metal-free "click chemistry" with the peptide Tyr-Ile-Gly-Ser-Arg (YIGSR). Fibers that were both aligned and functionalized with YIGSR were found to significantly increase the fraction of mouse embryonic stem cells (mESC) expressing neuron-specific class III beta-tubulin (TUJ1), the level of neurite extension and gene expression for neural markers compared to mESC cultured on random fiber mats and unfunctionalized matrices. Precise functionalization of degradable polymers with bioactive peptides created translationally-relevant materials that capitalize on the advantages of both synthetic and natural systems, while mitigating the classic limitations of each.
Although a number of combinatorial/high-throughput approaches have been developed for biomaterial... more Although a number of combinatorial/high-throughput approaches have been developed for biomaterial hydrogel optimization, a gradient sample approach is particularly well suited to identify hydrogel property thresholds that alter cellular behavior in response to interacting with the hydrogel due to reduced variation in material preparation and the ability to screen biological response over a range instead of discrete samples each containing only one condition. This review highlights recent work on cell–hydrogel interactions using a gradient material sample approach. Fabrication strategies for composition, material and mechanical property, and bioactive signaling gradient hydrogels that can be used to examine cell–hydrogel interactions will be discussed. The effects of gradients in hydrogel samples on cellular adhesion, migration, proliferation, and differentiation will then be examined, providing an assessment of the current state of the field and the potential of wider use of the gradient sample approach to accelerate our understanding of matrices on cellular behavior.
Volumetric muscle defect, caused by trauma or combat injuries, is a major health concern leading ... more Volumetric muscle defect, caused by trauma or combat injuries, is a major health concern leading to severe morbidity. It is characterized by partial or full thickness loss of muscle and its bio-scaffold, resulting in extensive fibrosis and scar formation. Therefore, the ideal therapeutic option is to use stem cells combined with bioscaffolds to restore muscle. For this purpose, muscle-derived stem cells (MDSCs) are a great candidate due to their unique multi-lineage differentiation potential. In this study, we evaluated the regeneration potential of MDSCs for muscle loss repair using a novel in situ fibrin gel casting. Muscle defect was created by a partial thickness wedge resection in the tibialis anterior (TA) muscles of NSG mice which created an average of 25% mass loss. If untreated, this defect leads to severe muscle fibrosis. Next, MDSCs were delivered using a novel in situ fibrin gel casting method. Our results demonstrated MDSCs are able to engraft and form new myofibers in the defect when casted along with fibrin gel. LacZ labeled MDSCs were able to differentiate efficiently into new myofibers and significantly increase muscle mass. This was also accompanied by significant reduction of fibrotic tissue in the engrafted muscles. Furthermore, transplanted cells also contributed to new vessel formation and satellite cell seeding. These results confirmed the therapeutic potential of MDSCs and feasibility of direct in situ casting of fibrin/MDSC mixture to repair muscle mass defects.
Combinatorial method/high throughput strategies, which have long been used in the pharmaceutical ... more Combinatorial method/high throughput strategies, which have long been used in the pharmaceutical industry, have recently been applied to hydrogel optimization for tissue engineering applications. Although many combinatorial methods have been developed, few are suitable for use in tissue engineering hydrogel optimization. Currently, only three approaches (design of experiment, arrays and continuous gradients) have been utilized. This review highlights recent work with each approach. The benefits and disadvantages of design of experiment, array and continuous gradient approaches depending on study objectives and the general advantages of using combinatorial methods for hydrogel optimization over traditional optimization strategies will be discussed. Fabrication considerations for combinatorial method/high throughput samples will additionally be addressed to provide an assessment of the current state of the field, and potential future contributions to expedited material optimization and design.
Journal of biomedical materials research. Part A, Jan 26, 2017
Many studies have utilized Irgacure 2959 photopolymerized poly(ethylene glycol) (PEG) hydrogels f... more Many studies have utilized Irgacure 2959 photopolymerized poly(ethylene glycol) (PEG) hydrogels for tissue engineering application development. Due to the limited penetration of ultraviolet light through tissue, Irgacure 2959 polymerized hydrogels are not suitable for use in tissues where material injection is desirable, such as the spinal cord. To address this, several free radical initiators (thermal initiator VA044, ammonium persulfate (APS)/TEMED reduction-oxidation reaction, and Fenton chemistry) are evaluated for their effects on the material and mechanical properties of PEG hydrogels compared with Irgacure 2959. To emulate the effects of endogenous thiols on in vivo polymerization, the effects of chain transfer agent (CTA) dithiothreitol on gelation rates, material properties, Young's and shear modulus, are examined. Mouse embryonic stem cells and human induced pluripotent stem cell derived neural stem cells were used to investigate the cytocompatibility of each polymeriz...
Acta biomaterialia, 2016
N-cadherin cell-cell signaling plays a key role in the structure and function of the nervous syst... more N-cadherin cell-cell signaling plays a key role in the structure and function of the nervous system. However, few studies have incorporated bioactive signaling from n-cadherin into tissue engineering matrices. The present study uses a continuous gradient approach in polyethylene glycol dimethacrylate hydrogels to identify concentration dependent effects of n-cadherin peptide, His-Ala-Val-Asp-Lle (HAVDI), on murine embryonic stem cell survival and neural differentiation. The n-cadherin peptide was found to affect the expression of pluripotency marker, alkaline phosphatase, in murine embryonic stem cells cultured on n-cadherin peptide containing hydrogels in a concentration dependent manner. Increasing n-cadherin peptide concentrations in the hydrogels elicited a biphasic response in neurite extension length and mRNA expression of neural differentiation marker, neuron-specific class III β-tubulin, in murine embryonic stem cells cultured on the hydrogels. High concentrations of n-cadhe...
Journal of biomedical materials research. Part A, Jan 31, 2016
Mechanotransduction in neural cells involves multiple signaling pathways that are not fully under... more Mechanotransduction in neural cells involves multiple signaling pathways that are not fully understood. Differences in lineage and maturation state are suggested causes for conflicting reports on neural cell mechanosensitivity. In order to optimize matrices for use in stem cell therapy treatments transplanting human induced pluripotent stem cell derived neural stem cells (hNSC) into lesions after spinal cord injury, the effects of Young's Modulus changes on hNSC behavior must be understood. The present study utilizes polyethylene glycol hydrogels containing a continuous gradient in Young's modulus to examine changes in the Young's Modulus of the culture substrate on hNSC neurite extension and neural differentiation. Changes in the Young's Modulus of the polyethylene glycol hydrogels was found to affect neurite extension and cellular organization on the matrices. hNSC cultured on 907 Pa hydrogels were found to extend longer neurites than hNSC cultured on other tested ...
Acta Biomaterialia, 2015
Stem cell therapies, which aim to restore neurological function after central nervous system inju... more Stem cell therapies, which aim to restore neurological function after central nervous system injury, have shown increased efficacy when a tissue engineering matrix is implanted with cells compared to implantation of the cells alone. However, much work still needs to be done to characterize materials that can be used to facilitate and direct the differentiation of implanted cells. In the current study, polyethylene glycol hydrogels functionalized with continuous Ile-Lys-Val-Ala-Val (IKVAV) concentration gradients were fabricated and utilized to systematically study and optimize the adhesive conditions for neural differentiation of mouse embryonic stem cells in two- and three-dimensional environments. The results suggest that 570μM and 60μM are the optimal IKVAV concentrations for 2D and 3D neural differentiation, respectively, to maximize mRNA expression of neuron-specific markers and neurite extension while minimizing apoptotic activities in cultured cells compared to those exposed to higher IKVAV concentrations. The combinatorial approach presented in this work demonstrates that hydrogels functionalized with bioactive peptides provide a defined and tunable platform that can be employed to characterize and improve culture conditions for superior survival, maturation and integration of implanted cells, leading to enhanced restoration of neurological function for those receiving stem cell therapies after traumatic brain and spinal cord injuries.
Biomacromolecules, Jan 5, 2015
Amino acid-based poly(ester urea)s (PEU) are high modulus, resorbable polymers with many potentia... more Amino acid-based poly(ester urea)s (PEU) are high modulus, resorbable polymers with many potential uses, including the surgical repair of bone defects. In vitro and in vivo studies have previously shown that phenylalanine-based PEUs have non-toxic hydrolytic byproducts, and tunable degradation times. Phenylalanine PEUs (poly(1-PHE-6)) have been further modified by tethering osteogenic growth peptide (OGP) to tyrosine-based monomer subunits. These OGP-tethered PEUs have been fabricated into porous scaffolds and cultured in vitro to examine their effect on differentiation of human mesenchymal stem cells (hMSCs) toward the osteogenic lineage. The influence of tethered OGP on the hMSC proliferation and differentiation profile was measured using immunohistochemistry, biochemistry, and quantitative real time polymerase chain reaction (qRT-PCR). In vitro data shows that the OGP-tethered scaffolds show enhanced BSP expression (~130-160% increase) by 2 weeks compared to control scaffolds lac...
MRS Proceedings, 2004
... Fabrication Victor J. Chen, 1 Laura A. Smith, 1 and Peter X. Ma 1-3 1 Department of Biomedica... more ... Fabrication Victor J. Chen, 1 Laura A. Smith, 1 and Peter X. Ma 1-3 1 Department of Biomedical Engineering, 2 Biologic and Materials Sciences, and ... 2001). 7. SF Yang, KF Leong, ZH Du, and CK Chua, Tissue Engineering 7 (6), 679 (2001). ...
Online, 2007
Page 1. Nanotechnologies for the Life Sciences Vol. 9 Tissue, Cell and Organ Engineering. Edited ... more Page 1. Nanotechnologies for the Life Sciences Vol. 9 Tissue, Cell and Organ Engineering. Edited by Challa SSR Kumar Copyright 8 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN: 3-527-31389-3 4 Nanofibrous Scaffolds and their Biological Effects ...
The synthesis of a 4-dibenzocyclooctynol (DIBO) functionalized polyethylene glycol (PEG) and fabr... more The synthesis of a 4-dibenzocyclooctynol (DIBO) functionalized polyethylene glycol (PEG) and fabrication of hydrogels via strain-promoted, metal-free, azide-alkyne cycloaddition is reported. The resulting hydrogel materials provide a versatile alternative in which to encapsulate cells that are sensitive to photochemical or chemical crosslinking mechanisms.
Nano-fibrous scaffolding mimics aspects of the extracellular matrix to improve cell function and ... more Nano-fibrous scaffolding mimics aspects of the extracellular matrix to improve cell function and tissue formation. Although several methods exist to fabricate nano-fibrous scaffolds, the combination of phase separation with reverse solid freeform fabrication (SFF) allows for scaffolds with features at three different orders of magnitude to be formed, which is not easily achieved with other nano-fiber fabrication methods. This technique allows for the external shape and internal pore structure to be precisely controlled in an easily repeatable manner, while the nano-fibrous wall architecture facilitates cellular attachment, proliferation, and differentiation of the cells. In this chapter, we examine the fabrication of computer-designed nano-fibrous scaffolds utilizing thermally induced phase separation and reverse SFF, and the benefits of such scaffolds over more traditional tissue engineering scaffolds on cellular function and tissue regeneration.
Wiley Interdisciplinary Reviews-Nanomedicine and Nanobiotechnology, 2009
The structural features of tissue engineering scaffolds affect cell response and must be engineer... more The structural features of tissue engineering scaffolds affect cell response and must be engineered to support cell adhesion, proliferation and differentiation. The scaffold acts as an interim synthetic extracellular matrix (ECM) that cells interact prior to forming new tissue. In this review, bone tissue engineering is used as the primary example because of our group's focus and for the sake of brevity. We focus on nano-fibrous scaffolds and the incorporation of other components including other nanofeatures into the scaffold structure. Since the ECM is comprised in large part of collagen fibers, between 50-500 nm in diameter, well-designed nano-fibrous scaffolds mimic this structure. Our group has developed a novel thermally-induced phase separation (TIPS) process in which a solution of biodegradable polymer is cast into a porous scaffold, resulting in a nano-fibrous pore-wall structure. These nano-scale fibers have a diameter (50-500 nm) comparable to those collagen fibers found in the ECM. This process can then be combined with a porogen leaching technique, also developed by our group, to engineer an interconnected pore structure that promotes cell migration and tissue ingrowth in three dimensions. To improve upon efforts to incorporate a ceramic component into polymer scaffolds by mixing, our group has also developed a technique where apatite crystals are grown onto biodegradable polymer scaffolds by soaking them in simulated body fluid (SBF). By changing the polymer used, the concentration of ions in the SBF and by varying the treatment time, the size and distribution of these crystals is varied. Work is currently being done to improve the distribution of these crystals throughout three-dimensional scaffolds and to create nano-scale apatite deposits that better mimic those found in the ECM. In both nano-fibrous and composite scaffolds, cell adhesion, proliferation and differentiation improved when compared to control scaffolds. Additionally, composite scaffolds showed a decrease in incidence of apoptosis when compared to polymer control in bone tissue engineering. Nanoparticles have been integrated into the nanostructured scaffolds to deliver biologically active molecules such as growth and differentiation factors to regulate cell behavior for optimal tissue regeneration.
Biomaterials Science, 2013
ABSTRACT Cell sourcing continues to be a significant limitation to regenerative medicine especial... more ABSTRACT Cell sourcing continues to be a significant limitation to regenerative medicine especially in neural lineages where population heterogeneity during in vitro culture prevents definitive phenotype assessment. For nearly 40 years, the biological community has worked with amine-derivated surfaces and hydrogels, especially alginate, with little quantitative assessment of how local amine concentration influences the extent of neural differentiation and neurite extension. In this manuscript we show that the local concentration of amines distinctly influences mouse embryonic stem cell (ESC) lineage commitment and the length of neurite extensions both of which are early indicators of differentiation. The well-defined amine gradients are a highly relevant tool for identifying these critical concentrations and thresholds. We feel these results will be of critical importance to researchers developing new ex vivo culture materials for neural applications as well as the community exploring nerve regeneration in vivo.
Tissue Engineering Part A, 2010
One of the major challenges to the application of human embryonic stem cells (hESCs) to the repai... more One of the major challenges to the application of human embryonic stem cells (hESCs) to the repair of defective tissues is the directed differentiation of cells into specific lineages to avoid the formation of inferior heterogeneous tissues. To accomplish this goal, the lineage-specific stem cell population needs to be isolated and optimal differentiation conditions need to be defined. In this study, homogenous hESC-derived mesenchymal stem cells (hESC-MSCs) were generated and used to construct bone tissue. The effect of osteogenic factors, including dexamethasone (Dex) and bone morphogenetic protein-7 (BMP-7), on the osteogenesis of hESC-MSCs was investigated. It was found that BMP-7 itself had little effect on the in vitro osteogenic differentiation of hESC-MSCs; however, there was a synergic effect between BMP-7 and Dex in promoting osteogenesis. The effect of osteoconductive nanofibrous polylactic acid material on osteogenesis of hESC-MSCs was also investigated. It was found that the nanofibrous matrix architecture promoted alkaline phosphatase activity and calcium deposition of cells cultured under osteogenic conditions. Based on these findings, the hESC-MSCs were cultured on threedimensional nanofibrous scaffolds in combination with Dex and BMP-7 stimulation in vitro to generate bone-like tissues. After 6 weeks of culture, highly mineralized tissues developed with specific bone marker genes expressed. These data illustrate the promise of hESC-MSCs for bone regeneration under optimal conditions.
Tissue Engineering Part A, 2009
Controlled differentiation of embryonic stem cells (ESC) is necessary to their use as a cell sour... more Controlled differentiation of embryonic stem cells (ESC) is necessary to their use as a cell source for tissue engineering or regeneration. To date, most studies have concentrated on chemical cues to direct ESC differentiation. However, during normal embryonic development, multiple factors beyond chemical cues play a role, including the extracellular matrix (ECM) in bone development. In this study, we use nanofibrous (NF) matrices to mimic the morphology of the ECM to examine the contribution of the ECM morphology to the differentiation of mouse ESC. After 12 h of differentiation culture, mouse ESC form protrusions interacting with NF matrices, while they appear not to interact with flat films. Immunofluorescence staining after 26 days of differentiation culture indicates a greater degree of differentiation for mouse ESC on NF matrices compared to flat films. Polymerase chain reaction results, also, show greater degree of osteogenic differentiation on NF matrices compared to flat films when osteogenic supplements are added to the culture. Overall, these results demonstrate that NF morphology contributes to the controlled differentiation of mouse ESC.
Colloids and Surfaces B: Biointerfaces, 2004
Biomaterials, 2013
End-functional PLLA nanofibers were fabricated into mats of random or aligned fibers and function... more End-functional PLLA nanofibers were fabricated into mats of random or aligned fibers and functionalized post-spinning using metal-free "click chemistry" with the peptide Tyr-Ile-Gly-Ser-Arg (YIGSR). Fibers that were both aligned and functionalized with YIGSR were found to significantly increase the fraction of mouse embryonic stem cells (mESC) expressing neuron-specific class III beta-tubulin (TUJ1), the level of neurite extension and gene expression for neural markers compared to mESC cultured on random fiber mats and unfunctionalized matrices. Precise functionalization of degradable polymers with bioactive peptides created translationally-relevant materials that capitalize on the advantages of both synthetic and natural systems, while mitigating the classic limitations of each.